This invention relates generally to a FSK demodulation circuit of the type used in communication networks employing binary transmission signals and more particularly to a FSK demodulation circuit which reliably detects signals having low signal to noise ratio with minimum distortion. There are well-known FSK demodulation circuits such as the frequency discriminator type, zero-crossing type, differential demodulation type and phase-locked loop type (PLL). However, because when analog circuit techniques are employed, the FSK demodulation circuits include a large number of components and consequently are often in need of adjustment. Further, the circuit is large in size, high in production cost and long term reliability of operation is low. Of great significance, such circuits cannot be fully integrated for miniaturization.
What is needed is a FSK demodulation circuit which provides excellent detection of low signal to noise ratio communications, with low distortion and by means of an entirely integrated circuit.